Various air operated, double acting, piston pumps having poppet valves mounted in the inlet and the outlet of the pump have been proposed, as evidenced by U.S. Pat. Nos. 2,239,727; 2,699,153; 3,256,827; 3,622,250; and 5,094,596.
While these pumps have been generally satisfactory for their intended purposes, they are designed to pump relatively light, clean fluids. If an attempt was made to pump viscous sludges and slurries, or fluid contaminated with sand, rocks, rags, and the like, it has been found that the debris in the fluid being pumped has a tendency to collect around the seat of the poppet valves; thereby preventing a proper seating of the valves, and the construction and arrangement of the pump housing is such that the debris gets stuck or lodged in the housing, thereby rendering the pump inoperative.
To overcome the disadvantages experienced with air operated, double acting piston pumps having poppet valves mounted in the inlet and the outlet of the pump, the pump of the present invention has been devised so that not only can light clean fluids be pumped but also sludges, slurries and fluid contaminated with debris such as sand, rocks, rags, and the like.